I think it all comes down to your view of the nature and purpose of human existence. Which is a very large issue I'm not prepared to go into at the moment.
Suffice it to say for now that, if one's view is that 'We are but dust' -- nothing more -- then any value we care to assign to human life is effectively negated and there can be no special reason not to terminate our lives as and when we see fit.
I don't buy the view that 'We are but dust', BTW.
